The present invention relates to an apparatus and method for forming panels, such as protective and sound suppressing liners, from moldable materials. Such liners are primarily used for aircraft engines but can be used in a variety of industries where sound suppression or protection from flying objects is needed. In the aircraft industry, panels made by the apparatus and method of this invention are primarily used to suppress sound and to protect aircraft and aircraft engines from ice that is thrown off the fan blades of ducted aircraft engines, such as gas turbine engines.
Prior to this invention, the panels used in the liners were manufactured by hand packing a dry thixotropic paste into a mold cavity. The moldable material usually used has the consistency of dry spackling compound. The material is smoothed with a cylindrical piece of aluminum and shaved to the proper dimensional height using a sharp spatula. This methodology presents several problems in producing dimensionally consistent and correct panels. In addition the material usually used can be hazardous, and, therefore, hand working of the material is not desirable.
When hand packing the moldable material, a polytetrafluoroethylene tape is used to coat the mold surface and keep the moldable material from sticking to the mold surface during elevated temperature cure. The use of conventional polytetrafluoroethylene film is not possible due to molding pressure and manipulation of the material, which tears and wrinkles the polytetrafluoroethylene film. Any tears or wrinkles translate to a similar appearance in the part, and are considered as a nonconformance to engineering specifications. The use of polytetrafluoroethylene tape can be very time consuming in that its application has to be seamless and without wrinkles. This is difficult to achieve in a contoured mold cavity.
These issues can lead to a final product that varies in quality and, particularly, in thickness. Parts that do not meet thickness requirements have to be repaired at significant cost or, in some cases, scrapped. Hand packing can also leave non-filled cavities that have to be repaired. Thus there is a need for an improved apparatus and process for forming panels from moldable material.